PID autotune fails for hotend

my heater was too weak to operate at higher temperatures, so I build a heater block for two heaters.
On first test the heater didn't stop at given temperature but jumped over 300°C - so I searched for pid tuning.

is telling you that the heater power is much too high. The values it gives may be correct for your hot end, but the firmware regards a gain (A parameter) above 1500 as indicating that something went wrong.